DNA, RNA contaminants
 Contaminants

[2012 Sept] Fragments of Foreign DNA and Other Substances From Vaccines Found in Disabled and Dying Children by Christina England

[2012 Sept] Unveiling the Culprit – Is Foreign DNA Contamination the Autistic Villain behind Biologic Vaccine Injuries? By Leslie Carol Botha

Genetically engineered vaccines 'Inherently unpredictable and possibly dangerous'

There is the problem of DNA & RNA contamination of vaccines